The present invention relates to a guide roller appropriate to restrict the position of a magnetic tape being moved in contact with the guide roller in a video cassette recorder, for example.
FIG. 3 is a partially sectional view of a conventional guide roller of such kind. The guide roller comprises a shaft 1, a rotary body 2 fitted around the shaft coaxially thereto, an attaching ring 4 formed with a male screw thread 3 and mounted on the shaft coaxially thereto, a flange 7 having slits 6, and a flange 8 having a through-hole. The attaching ring 4 is mounted on the shaft 1 after the rotary body 2 is fitted around the shaft. The rotary body 2 is constructed by rotary & cylinder 5 made of a resin, which constitutes the tape guide surface of the guide roller. When the rotary body 2 is fitted around the shaft 1, the flange 7 is first secured to the shaft at the upper end thereof and then turned upside down together with the shaft, and the flange 8 is thereafter press-fitted on the shaft over the cylinder and located so that the rotary cylinder can be smoothly rotated. After that, the attaching ring 4 is press-fitted on the shaft 1 through the use of a jig. For example, the guide roller is set up on the metal base of a video tape recorder at a prescribed angle thereto. The metal base has a tapped hole in which the male screw thread 3 of the attaching ring 4 is fixed. The flat bit of a screwdriver is inserted into the slits 6 of the flange 7 and rotated to turn the whole of the guide roller to tighten the male screw thread so as to adjust the height of the guide roller relative to the metal base.
When a magnetic tape is moved in contact with the tape guide surface of the guide roller, the rotary cylinder 5 is rotated at a substantially constant speed. The constant speed movement of the rotary cylinder 5 effects to absorb the vibration of the magnetic tape being moved in contact with the tape guide surface of the guide roller. The larger the inertial moment of the rotary cylinder 5 has the higher the vibration absorbing effect of the movement thereof. However, since the conventional rotary cylinder 5 is made of only the resin, the diameter thereof needs to be increased if the inertial moment thereof is to be augmented. In other words, the conventional guide roller is disadvantageous that if the inertial moment of the rotary cylinder 5 is to be augmented, the guide roller may become greater than average in large size.